September 8, 2011
Last time, we looked at the bones of the sauropod skeleton, and I mentioned that “thanks to the wonder of homology, it doubles as a primer for dinosaur skeletons in general”. To prove it, here everyone’s favourite vulgar, overstudied theropod Tyrannosaurus rex, in L. M. Sterling’s reconstruction from Osborn 1906:plate XXIV, published just one year after the big guy’s initial description. (The pose is somewhat outdated, but it’s a classic):
Click through for the full-sized version (2897 by 1755 pixels), which — like yesterday’s Camarasaurus — you are welcome to print out and hang on your wall as a handy reference. (Sterling’s original is out of copyright; I hereby make my modified version available under the CC-BY-NC-SA licence.)
The thing to notice is that the Camarasaurus and Tyrannosaurus have exactly the same bones, excepting only that theropods had gastralia (belly ribs) and sauropods probably did not. If you doubt it, here are the two animals composited together. Print it out! Print lots of copies! Hand them out to your friends!
September 7, 2011
We should have done this long ago. Back in the early tutorials, we covered skeletal details such as regions of the vertebral column, basic vertebral anatomy, pneumaticity and laminae, but we never started out with an overview of the sauropod skeleton.
Time to fix that. This is numbered as Tutorial 15 but you can think of it as Tutorial Zero if you prefer. Thanks to the wonder of homology, it doubles as a primer for dinosaur skeletons in general.
Here is a complete, labelled sauropod skeleton, modified from Erwin S. Christman’s reconstruction of Camarasurus supremus in Ostrom and Mook 1921:plate LXXXIV:
Click through for the full-sized version (2897 by 1280 pixels), which you are welcome to print out and hang on your wall as a handy reference. (Christman’s original is out of copyright; I hereby make my modified version available under the CC-BY-NC-SA licence.)
Since that’s a lot to take in all at once, we’ll walk through the regions of the skeleton: the head and neck, the rest of the vertebral column, the forelimb and girdle, and the hindlimb and girdle. But first, a little bit of …
Skeletons consist of bones. The study of skeletons and of bones is called osteology. There are several ways of dividing up the skeleton into manageable chunks. One is to consider cranial vs. postcranial bones. In this division, cranium just means skull (though see below) and postcranium means “everything except the skull”. Here at SV-POW!, of course, we consider skulls beneath our notice, so this division seems silly to us. We have been known to refer to the skull as the prepostcranium on occasion.
A more useful division of the skeleton is into axial and appendicular. The axial skeleton includes the skull, hyoid apparatus (little bones in the neck that anchor tongue and throat muscles), vertebrae, ribs and chevrons (i.e. everything on the midline), and the appendicular bones are those of the limbs and their girdles, i.e. shoulders and hips. (I learned only very recently that, although they seem to be part of the forelimb girdle, the sternal plates are actually part of the axial skeleton, being related to the ribs rather than the shoulders.)
Head and neck
Let’s start with the head. Although “cranium” is sometimes used to mean the whole head, as noted above, it more strictly refers to the rigid upper portion of the skull which attaches to the neck and includes the upper jaw. The lower jar, which moves independently, is called the mandible. Both of these units are made up of many smaller bones. There is of course much, much more to say about skull anatomy, but that is another tutorial for another day. For now, we will just pretend that the skull is made of two lumps of bone and move swiftly onwards.
The back of the skull articulates with the neck, which is part of the spine, or vertebral column. All vertebrates have a spine; and in all tetrapods it’s divided into neck, trunk (or torso), sacrum and tail. The spine is composed of vertebrae: those in the neck are called cervical vertebrae, or cervicals for short; those in the trunk are called dorsal vertebrae (in crocs and mammals these are further broken down into the thoracic vertebrae, which bear mobile ribs, and the lumbar vertebrae which do not); those in the sacrum are called sacral vertebrae and those in the tail are called caudal vertebrae. But you already know that if you read Tutorial 1.
In some kinds of tetrapods, including all dinosaurs, the cervical vertebrae have backward-pointing ribs; these are called the cervical ribs. Birds have these (in reduced form) and so do crocs and mammals, but they are absent in at least some lizards and turtles. Contrary to popular belief, mammals do have bicipital (two-headed) cervical ribs, they are just very short and fused to the vertebrae. Even most human osteology textbooks refer to them as transverse process. But developmentally and functionally they are ribs; they bound the transverse foramina through which the vertebral arteries pass, and they anchor deep neck muscles. The “cervical ribs” that occasionally crop up as a pathology in humans are large, mobile, thoracic-style ribs, and represent segmentation anomalies during early development.
The cervical vertebrae are numbered backwards from the head. Each cervical can be identified by number, so that the tenth is called “cervical 10”, or C10 for short. Sauropods have between eleven and nineteen cervicals — a lot more than the feeble seven that nearly all mammals have, but well short of the seventy or so that Elasmosaurus could boast.
In most tetrapods, the cervicals from C3 backwards are similar in shape, although they tend to get bigger as they approach the torso; but the first two are distinctive, so they have special names. C1 is called the atlas — easy to remember as it holds up the head, just as the titan Atlas held up the sky (not the Earth as often thought). It doesn’t really look like a vertebra at all, being ring-shaped and (in sauropods) tiny. C2 is called the axis. It looks much more like a normal vertebra, but has an odd articulation at the front, a distinctive blunt spike that the atlas sits on (it also has small prezygapophyses for the neural arch elements of the atlas–these little bits of bone are often lost in fossil skeletons). It’s smaller than the succeeding vertebrae — unlike the situation in mammals, in which the axis is ususally the largest cervical — and has a big, blade-like neural spine.
Torso and tail
The vertebral column continues back from the base of the neck, as the torso, which consists of dorsal vertebrae.
In the region of the hips, several vertebrae fuse together: this is true to some extent in most or all tetrapods, but in many groups it’s only two or three vertebrae that fuse, whereas in sauropods (and most dinosaurs) it’s four or more. This set of fused vertebrae is the sacrum, and the vertebrae that make it up are the sacral vertebrae.
Behind the sacrum is the tail, which is composed of caudal vertebrae. Hanging beneath these — or, specifically, between the intervertebral joints — are transversely flattened bones called chevrons or haemopophyses. These exist in most reptiles, but have been lost in most mammals. (They do exist in wallabies, but they are a very different shape.) Developmentally the chevrons mirror the neural arch, and form a canal for the caudal aorta in the same way that the neural arch forms a canal for the spinal cord.
Just as the cervical vertebrae have cervical ribs, so the dorsal vertebrae have dorsal ribs. These are longer and more vertically oriented than the cervical ribs. The sacral vertebrae, too, have sacral ribs, but you rarely see them because in lateral view they are obscured by the ilium — as is the case here. You might, then, wonder whether the caudal vertebrae have caudal ribs, but the answer is not clear. The first few caudals, at least, do have lateral processes, but surprisingly there is no consensus about what they actually are: ribs that are fused to the vertebrae, or paraphophyses/diapophyses that are fused together. See the overview in Wilson (1999:642).
How can you tell where the neck ends are the torso begins? The traditional answer is that the first dorsal vertebrae is the first one with a “free” (i.e. unfused) rib, but it’s not always that clear. Although cervical ribs generally fuse to their vertebrae and dorsal ribs rarely or never do, there are plenty of exceptions — for example, the last few cervical ribs of the Mamenchisaurus hochuanensis holotype appear unfused. Also, in specimens where the cervicodorsal transition is well preserved, it’s apparent that the switch from short backward-directed cervical ribs to long downward-directed dorsal ribs may be abrupt, between adjacent vertebrae, or a gradual transition spread out over several vertebrae. Since the shoulder girdle bones don’t articulate with the torso, that clue’s also unavailable, so all in all it can be hard to nail down where the transition was. You just sort of know it when you see it.
The final axial bones are the sternal plates, which belong somewhere in the breast area. The exact placement and orientation of these bones is not agreed, and they are rarely if ever preserved in place.
Shoulder and forelimb
The bones of the shoulder are the elongate scapula, or shoulder-blade, on the side of the torso; and the coracoid, lower down wrapping round to the front. Together, these bones make up the shoulder girdle. Unlike the pelvis, the shoulder is not fused to the bones of the torso, but would have been bound to it by ligament and muscle. Because of this, the exact position of the scapula and coracoid are not known, and remain the subject of controversy. The reconstruction above shows a fairly vertical scapula; some others make it more nearly horizontal.
Where the scapula and coracoid meet, they form a hollow on the underside, called the glenoid. The head of the humerus fits in here; two parallel bones form the lower limb segment: the ulna and radius. In sauropods, the ulna is a rounded triangle in cross-section, with a hollow on the front face of the triangle which the radius fits into.
At the bottom of the lower limb segment are the carpals, or wrist bones; then the manus, or hand. The upper bones of the manus are the metacarpals, which in sauropods are held near-vertical in a semi-circular arcade with the hollow directed backwards and slightly inwards. Below the metacarpals are the phalanges (singular phalanx); each finger may have multiple phalanges, but sauropods tend to have very few. When the last phalax of a digit is claw-shaped, it’s called an ungual.
Because both forefeet and hindfeet have phalanges and unguals, we distinguish by saying manual phalanges and manual unguals for the bones of the forelimb, and pedal phalanges and pedal unguals for those of the hindlimb.
Hip and hindlimb
The pelvis, or hip girdle, is made up of three bones on each side: the ilium, on top, is roughly semi-circular; the pubis, at the front, and the ischium, at the back, are more elongate. Where these three bones meet, they form a circular hole called the acetabulum, or hip socket. Unlike the shoulder girdle, the pelvis is fused to the torso: specifically, the ilium is fused to the sacrum via the transverse processes of the sacral vertebrae and their sacral ribs. The pubes and ischia do not fuse.
The femur, or thigh bone, has a head that projects into the acetabulum. At the knee, it meets two parallel lower-limb bones, the tibia and fibula. The former is the main weight-bearing bone and is nearest the midline. The fibula sits to the side of it. Unlike mammals, most reptiles including non-avian dinosaurs have no kneecap, or patella; but birds do. Sesamoids or “floating” bones like the patella seem to be evolved and lost more readily than the normally-connected bones of the skeleton.
Below these two bones are the tarsals, or ankle bones. In sauropods there are one or two of these: a large, disc-shaped astragalus beneath the tibia, and sometimes a smaller globular calcaneum below the fibula. (For some reason, the carpals don’t seem to have names.) Beneath these is the pes, or hindfoot. The upper bones of the pes are the elongate metatarsals. Beyond these are the short pedal phalanges and unguals.
What did we miss?
The bones listed account for nearly all the skeleton. There are, however, a few extra bones that are rarely recovered or not always present. Clavicles, or collar bones, have been reported in the limb girdles of some sauropods. Gastralia, or belly ribs, were probably present in all sauropods, but are fragile and very rarely preserved. Finally, some sauropods had osteoderms — small, isolated bones embedded in the skin and serving as armour. None of these are illustrated in Christman’s Camarasaurus.
Because the basic tetrapod body-plan is so conservative — many bones change size and shape, but it’s comparatively rare for bones to evolve away or for new ones to evolve — you can look at skeletons of all sorts of animals in a museum and recognise nearly all the bones I’ve listed here. Birds, the closest living relatives of sauropods, have everything I’ve listed here, though their sternal plates have merged into a single big sternum and their forelimbs are obviously highly modified. Crocs have everything. Lizards have everything except cervical ribs. Even mammals are surprisingly similar, though all the pelvis bones fuse together and the coracoid is lost (the coracoid process of the scapula in humans and other mammals is a different, non-homologous bit of bone).
In particular, you have nearly all the bones in a sauropod skeleton, though of course many of the bones are very different in shape, or fused together, and your tail is contemptible. You might like to try re-reading this tutorial, finding all the relevant bones in your own body. You have a few extras as well: most obviously, your kneecaps, but also extra bones in the wrist and ankle.
SEE ALSO: the same thing done for Tyrannosaurus.
Wilson, Jeffrey A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Paleontology 19(4): 639-653. [Wilson used to have a freely available PDF on his site, but he seems to have removed it, and substituted a link to a paywalled PDF.]
July 20, 2011
This just in, forwarded to the ICZN mailing list by Donat Agosti:
At the Nomenclatur Section Meeting at the International Botanical Congress in Melbourne the decision passed, that e-only publications will be valid as of January 2012. The amendment passed by an overwhelming majority, well beyond the requested 60% yes vote.
This decision is contingent upon the confirmation by the IBC on Saturday July 30.
The language that passed is:
Publication is effected (..) Publication is also effected by electronic distribution of material in Portable Document Format (PDF, see also Rec. 29A.0) in a on online serial journal with an International Standard Serial Number (ISSN). [no guarantee for the exact language]
An amendment to include 10 hard copies has been turned down.
In short, this means that if you work on plants, you will be able, starting in January, to name new species in electronic-only publications such as PLoS ONE and Palaeontologia Electronica — publications that are becoming increasingly important due to their openness and easy accessibility.
This is great news for botanists.
Unfortunately, it doesn’t do anything (directly) for us zoologists.
Now is the time for the zoological code (ICZN) to follow suit! I’ve argued before — in the Bulletin of Zoological Nomenclature, no less — that electronic publication of nomenclatural acts is inevitable, and will be accepted by the taxonomic community with or without the endorsement of the Code: the botanical Code’s whole-hearted endorsement of this reality is further evidence that the ICZN’s current only-paper-counts stance is untenable now that we all live in the Shiny Digital Future.
At the time of writing the ICZN is still considering an amendment to recognise electronic publication. A draft amendment was published for comment in 2008, ultimately appearing in five journals (Zootaxa, African Invertebrates, Zoological Journal of the Linnean Society, Bulletin of Zoological Nomenclature, Journal of Crustacean Biology). Since then, six subsequent issues of BZN have included discussions of the issue, but so far as I can tell there is still no agreed text of the proposed amendment, let alone an actual change in the code. Since everyone else accepts electronic publication, the ICZN is in danger of making itself look anachonistic or even irrelevant. That would be a disaster for zoology: our discipline needs an accepted, respected, relevant code.
The ICZN must move now!
Update (9pm, the same day)
The story is covered by Nature, in a well written article by Daniel Cressey. Key quote: “Now the pressure is on zoologists to catch up with their botanical brethren”.
February 17, 2011
I have just made a series of fairly major edits to the in-progress Checklist for new zoological genera and species, and wanted to explain what’s changed and why.
The important change is that the Checklist no longer attempts to encompass the creation of families, nor of all genus-group and species-group names — only genera and species. I took this painful decision after a lot of consultation with various people, here and by email, despite wanting the utility of the Checklist to be a broad as possible. In the end, it became apparent that the attempt to include these other ranks could only result in the Checklist becoming much much longer and more complex, or leaving loopholes, or more likely both.
- The very terms “genus-group” and “species-group” are misleading to non-specialist taxonomists — they can easily be misunderstood as meaning “group of genera” and “group of species”.
- While the Code indicates that the only species-group ranks are species and subspecies, superspecies are fairly often used as well, and we don’t want to get into discussing such matters.
- Likewise, supergenera are sometimes used as well as genera, despite the lack of support in the Code.
- Conversely, the Code’s definition of genus-group names (see the Glossary) include things called “collective groups”, whatever they may be.
- Worse, the Code also talks about divisions, which are described in the Glossary, not particularly helpfully, as “(1) A rank that if treated as a division of a genus or subgenus is deemed to be of subgeneric rank for the purposes of nomenclature [Art. 10.4]. (2) A taxon at the rank of division.” We just don’t want to get into that stuff.
- Discussion of subgenera and related ranks on the ICZN mailing list has resulted in disagreement even between taxonomy specialists on that list, over matters such as whether a subgenus can be used as the type genus of a family. When even experts disagree, it seems a fool’s errand for the Checklist to try to tersely summarise the rules.
In short, I became convinced that trying to have the Checklist cover ranks other than genera and species opened up all sorts of cans of worms, and that the target audience — zoologists who are not taxonomy specialists — will get more value from a checklist that is more limited in scope, simpler to understand, and shorter.
As usual, comments are closed on this brief update — not to stifle debate, but because I want to keep all discussion together in one place: so please head over to the draft Checklist, read through the current version, and post any comments you may have.
I am optimistic that we are converging now on a version that is as simple as possible but no simpler. Once we freeze in a few days, we will hopefully move to the next phase … which I’ll tell you about at the time.
February 14, 2011
Sorry to bump Matt’s awesome Rhea-neck post off the top of the SV-POW! home page, but I have news of the rapidly developing checklist for new zoological names. As well as many, many minor and not-so-minor edits — and thanks to everyone who’s participated in this process — I have made a major structural change.
The list has been broken into two, first enumerating Requirements and then describing Best Practice. I have also reordered some of the points within lists. As a result, ALL NUMBERING HAS CHANGED; also some points have been split and others merged.
Please be sure to comment only on the most recent version.
I am worried that the Checklist is getting too big. I just copied and pasted the substance of it — the introductory paragraph and the two lists — into a new OpenOffice in 12-point Times, and found that it runs to a page and a quarter. Reduced to 10.5-point type it fits on a page, but that’s the way I want to go. So suggestions for reducing the length without losing content will be particularly welcome.
(As before, comments are closed on this post, because I don’t want to split discussion between here and the checklist itself.)
February 10, 2011
As we all know, the International Code of Zoological Nomenclature is a large and intimidating document. As a result, zoologists naming new animals often do not read it in its entirety (I know I haven’t). It’s probably because of this that many of the more avoidable nomenclatural mistakes occur.
Whatever might or might not eventually be possible in terms of simplifying the Code, everyone recognises that that would be a huge job, and something that would take years to do. So let’s ignore that possibility for now.
In the short term, what would be much more useful would be if someone could work up a very short document — no more than a single page of A4 and hopefully much shorter — that states in simple bullet-points what MUST be done to ensure that a new name is valid. Then there would be no excuse for zoologists venturing into nomenclature for the first time not to read such a document — let’s call it the ICZN Cheat Sheet.
Because it’s easier to steer a moving ship, I wrote to the ICZN email list this morning proposing an initial set of bullet points. I did not for a moment expect that they were complete, consistent or even necessarily correct; but I hoped that they could at least serve as a starting point for a very quick process of putting such a list together.
I am pleased to say that response on the list was fairly positive, and at the suggestion of one of the list members I have now posted the in-progress checklist as a page on this site, having revised it in accordance with several suggestions.
If you’re interested in contributing to this effort — helping us to derive a clear, concise and correct one-page guide to naming new zoological genera and species — please head over to the page and comment there. (Comments on this post are closed, to avoid splitting discussion across two places.)
October 9, 2010
I wasn’t going to write about this, partly because it’s so darn depressing, but mostly because in the wake of this comment it seemed like the “Amphicoelias brontodiplodocus” paper was being withdrawn, and to quote something Mike said off-list, I was happier about the retraction than I was sad about the implied revisionism. But then Henry Galliano wrote:
Although the paper has still not been completed, no changes have been made altering it conclusions. Interestingly, despite the 4000 recent hits and downloads from our website, it is surprising no evidence has been submitted challenging our claims.
If it’s really supposed to be an internal manuscript/press release type thing, why brag about the lack of criticism? Did it ever occur to you that we might be holding off out of respect, to give you an avenue of retreat where you could perhaps salvage a few scraps of dignity? But if you’re going to call us out for not tearing apart this joke of a paper, then stand by.
In the previous post, Mike wrote:
In other words, we’re being asked to believe that the new specimens are more different from all other Morrison diplodocids than any of them are from each other. And yet we’re brought to this conclusion by the very animals that are apparently not as similar. It’s as though I discovered dogs, and thereby concluded that lions, cheetahs and house-cats are are all the same species.
No, it’s way, way worse. Because, claims of the authors to the contrary, “Amphicoelias brontodiplodocus” is not some kind of morphological outlier among Morrison diplodocids. From where I stand, it looks like it’s right in the middle. So it’s as though I discovered ocelots and thereby concluded that lions, cheetahs, and housecats were all the same thing.
If no apatosaurs had ever been found, and they got the first one, and then concluded that all the apatosaurines were one taxon and all the diplodocines were another, that would at least make some kind of sense, in that they’d be drawing their taxonomic distinctions along actual phylogenetic lines. Then it would be a fairly straightforward lumper/splitter fight. In the actual event, I’m sad to say that it’s the “A. brontodiplodocus” proponents against the reality-based community.
Back to Henry’s statement about the “surprising” lack of evidence to the contrary: dude, don’t do this to yourself. We thought you were on the right track with the implied retraction from your earlier comment. You’ve been one of the white hats, but if you go down this dark path, forever will it dominate your destiny. Consume you it will!
It’s not at all “surprising” that no one has submitted evidence to the contrary. The evidence is in the 133 years’ worth of careful morphological and phylogenetic work that you blew right past on the way to nominating your new animal, at least implicitly, as TEH MOSTEST IMPORTANT DIPLODOCID EVAR!!11eleventy! Your material is awesome, and I don’t doubt that you’ve got a new animal on your hands, but the idea that it is one of only two diplodocids in the Morrison–or worldwide–and all the others are morphs of the same thing, is both suspiciously convenient for you, and so outrageously extreme that it would take a mountain of work (that is not presented in the paper) to demonstrate. In addition to the gross, obvious morphological differences, it would be really nice to know why there are geographic, stratigraphic, and paleoecological differences among the other Morrison diplodocids. Doesn’t the work of Dodson et al. (1980), Turner & Peterson (1999), and Foster (2003, 2007), just for starters, count for anything? Instead of boasting about the uncontested status of your claims, how about doing enough work to convince us to take them seriously in the first place? People who take the time to do reasonable morphological comparisons and phylogenetic work that doesn’t hail from an opium den have better things to do than exhaustively smack down every act of Hoser taxonomy that leaks onto teh intarwebz in the first two days. Give us a minute to get over our collective shock, and in the meantime, make up your mind about what the document is. Is it supposed to be considered published, or not? If so, it’s fair game for criticism, but don’t deny that you’re at least attempting acts of taxonomy. If not, don’t beg us to criticize it. You may get a lot more than you wished for.
Sadly, this will probably go down in popular opinion as a clash between academic and commercial paleontologists, or between credentialed paleontologists and hobbyists. It shouldn’t. I don’t care if someone is employed by a university or a rock shop, or whether they have any degrees in the field. All I care about is the quality of the work. (Repeatability, which necessitates that specimens be properly curated in accredited museums to ensure perpetual access to future researchers, is an inherent component of that quality.) Jack McIntosh is a physicist, and as far as I know never got any formal training in paleontology. But that’s irrelevant, because he taught himself by looking at literally thousands of specimens and reading everything he could get his hands on, and because his papers are as exhaustively researched as one could hope for. As Robert McKee wrote of Steven Pressfield, you can’t read Jack’s papers without being overwhelmed by “the work, the work, all the work” behind them. In contrast, I couldn’t read the “A. brontodiplodocus” paper without be overwhelmed by the complete disregard–and indeed implicit contempt–for all of the work that people from Cope and Marsh to Jerry Harris and David Lovelace have done on the admittedly knotty problem of Morrison sauropod diversity.
Taxonomy is facing a crisis, brought on by two things: at least for some charismatic clades, Hoser taxonomists potentially outnumber actual taxonomists (although even one is bad enough, as herpetologists have found); and there is essentially no filtering on what counts. Anyone in the world can whip up whatever uninformed BS they want and send a certain number of hardcopies off to libraries, and according to the ICZN their crappy work counts and the rest of us just have to deal with it. And the problem is only going to get worse in the shiny digital future as electronic publication removes the already minor inconvenience associated with “publishing” acts of taxonomy. I can think of a handful of possible outcomes:
- Working scientists are going to bog down in endlessly putting out the fires of Hoser taxonomy.
- We’ll install some kind of de jure filter to deal with Hoser taxonomy.
- We’ll collectively decide to ignore acts of Hoser taxonomy, which will constitute a de facto filter.
For my part, I think the ICZN’s policy of noninterference in cases like this is taking a sound principle to the point of lunacy. It’s like I walked up to a policeman, punched him in the nose, and told him he couldn’t arrest me because my assault counted as protected speech (on reflection, I’ll bet this actually happens in Berkeley). Of the options above, I suspect that we’ll end up with the third, and I won’t be entirely happy about that, because I also suspect that some credentialed academics will want to ignore the work of commercial paleontologists and hobbyists just because they’re not credentialed academics. Which would be wrong. We want to sort the work based on its quality, not who produced it.
Which is an interesting position for me to come to, given what I’ve said here in the past about filters. It was easier to deal with the thought of completely open publication when the waste products weren’t landing on my lawn. But I still think that this is the way things are going. In which case, post-hoc criticism of self-published works is often going to be the only filter we get. The comment thread is open. Filter away!
- Dodson, P., Behrensmeyer, A.K., Bakker, R.T., and McIntosh, J.S. 1980. Taphonomy and paleoecology of the dinosaur beds of the Jurassic Morrison Formation. Paleobiology 6:208-232.
- Foster, J.R. 2003. Paleoecological analysis of the vertebrate fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. New Mexico Museum of Natural History and Science. Bulletin 23.
- Foster, J.R. 2007. Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. 389pp.
- Turner, C.E., Peterson, F., 1999. Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, U.S.A. Pp. 77–114 in Gillette, D.D. (Ed.), Vertebrate Paleontology in Utah. Utah Geological Survey Miscellaneous Publication 99-1.